Rather than put a fuse on this furnace, an old Day & Night,
the manufacturer stuck a small fusible link in the wire
just before the heat exhanger limit switch. I amp'ed the
line while the furnace was operating with the main
gas valve open, burners burning, and it was less than
1 amp. My first inclination is to put a 3 amp blade fuse
inline rather than order the fusible link.
Does doing so sound good or bad? The board has no
other fuse for control voltage. I jumped it out
with a 5 amp fuse and the furnace worked for three
heat cycle attempts with the above amperage.
Based on the above, I am inclined to believe the
fusible link failed rather than really prevent a
real high current hazard.
The furnace is old, rusty, and could otherwise use
replacement, but that isn't my decision.